A total of 15 isolates of leishmania, most from patients seen or studied at NIH with cutaneous disease have been characterized as to biologic behavior in BALB/c mice. Many of these isolates have also been characterized by recent biochemical taxonomic methods. In the BALB/c mouse these isolates demonstrate a spectrum of biologic response, from failure to persist at the site of inoculation, to metastasis, visceratization and death. These well-characterized strains provide a useful resource for collaborative studies with others on temperature sensitivity, attack by lymphokines, models of muco-cutaneous disease, etc. Additional experience was gained with several patients using local heat for treatment of cutaneous leishmaniasis. The project on Chagas' disease progressed only with respect to (1) HLA tissue typingthat failed to indicate an association with disease and (2) a further inquiry into the significance of humoral suppression of lymphocyte proliferation to T cruzi antigen. The plaque characterization of T. cruzi strains was temporarily halted.